A mixture-compressing two-stroke Otto engine with fuel injection is known, in which a spherical combustion space eccentrically offset relative to the cylinder axis in the direction of the exhaust side and possessing an extension of approximately 260.degree. is disposed (DD-A1-228 585). It is known furthermore from the publication (DD-A1-3257) to dispose a cap-shaped combustion space centrally in the cylinder head. In both types an injection nozzle terminates in each case in the side of the cylinder opposite the exhaust duct, to be more precise, below the compression chamber formed in the upper compression point (OT) in a thermally less affected area.
In the spherical combustion space located in the cylinder head, which, in the direction of the cylinder head, possesses a heat-insulating shell section, the jet cone emitted by the injection nozzle of the injected fuel extends with a predominant proportion into the spherical combustion space and, with a small proportion, as far as the edge located on the cylinder space and the compression cross section. It is intended that this edge is cooled by the injected fuel being sprayed on to the same. It is true that the known arrangement ensures that the injection nozzle is less stressed thermally, however, the position of the combustion space which is offset toward the exhaust side with its constriction is not optimal for flushing with a fresh charge of fuel.
In the cap-shaped combustion space according to the publication DD-A1-3257, the jet cone of the injection nozzle is carried in such a manner that the entire combustion space and even partly the immediate vicinity of the spark plug projecting into the combustion space is covered by thr jet cone. However, in this case merely an oblique segment of the cylinder space is penetrated by the injection jet. Also in this known arrangement, the injection nozzle is not subjected to severe thermal stress. But the injection nozzle is located only a little above the upper edge of the exchaust duct. This calls for an early injection start while the exhaust duct is still open with the disadvantages resulting herefrom.
From the DE 39 04 760 A1, an Otto internal combustion engine with direct injection is known, in which a compression area between two compression area delimitation surfaces, which comprise a part of the piston bottom of the piston as well as a part of a lower surface area of the cylinder head and disposed in one half of the cylinder cross section is defined, wherein the compression area possesses a closed side delimited from a part of the internal surface of the cylinder bore as well a s an open side in the direction toward the center of the cylinder, in which case provision is made for the compression area, in the direction of the center of the cylinder to be expanded in such a way that a central portion of the open side of the compression area is disposed close to the cylinder center and in that the compression area, in the form of a flow of air in the cylinder, produces a compressed flow, which, in the position of the piston close to the compression point, assists the evaporation of the fuel in that the injection nozzle is disposed close to a central portion of the closed side of the compression area and is directed in such a manner that at least a part of the fuel is aimed at one of the compression area delimitation surfaces so that the fuel adhering to a compression area delimitation surface is assisted in its evaporation by the compressed flow and in that the spark plug is disposed near the ecnter of the cylinder as well so as to be located opposite the central portion of the open side of the compression area and ignites the evaporated fuel blown by the compressed flow toward the spark plug.
The U.S. Pat. No. 5,307,793 (D1) shows a mixture-compressing two-stroke Otto engine with fuel injection in the cylinder space of the following construction: Into a hemispherical combustion chamber offset eccentrically to the cylinder axis in the cylinder head, a spark plug projects, on both sides of the longitudinal plane of the exhaust duct, the overflow ducts terminate directed against the cylinder side oppositely located relative to the exhaust duct, an injection nozzle terminates in the cylinder side with the exhaust duct in a thermally less stressed zone outside the compression space, the injection takes place in the direction of the compression space, the combustion space is, with its combustion space axis, disposed so as to be offset from the cylinder axis in relation to the side of the cylinder located opposite the exhaust duct, in which case the injection nozzle is disposed relative to the combustion space in such a way that the upper portion of the jet cone penetrates a predominant volume proportion of the combustion space.